Revise examples in the intro to lists.
Revise examples in the intro to lists.

Also move sentence about .item immediately after code snippet where
it's first used. refs #2679

perl6/doc,perl6/doc,MasterDuke17/doc,tbrowder/doc,perl6/doc,MasterDuke17/doc,MasterDuke17/doc,perl6/doc,tbrowder/doc,MasterDuke17/doc,tbrowder/doc,perl6/doc,tbrowder/doc